1. Field of the Invention
The present invention relates to a communication control technique in an information processing apparatus.
2. Description of the Related Art
Conventionally, several methods have been proposed for implementing a diversity function of acquiring a signal with a high signal-to-noise ratio (SNR) using a plurality of antennas arranged in a space. In a method of implementing a diversity function with a simple configuration, one receiver system is built, and an antenna with a highest SNR is selected by switching an antenna switch for receiver input (see, e.g., Japanese Patent Laid-Open No. 6-303220).
When a wireless network complying with IEEE802.11 (to be referred to as a wireless LAN hereinafter) is used, generally, the SNR of a beacon periodically transmitted from an access point (AP) is used, and antenna evaluation is executed by comparing the SNRs of respective antennas. An antenna is selected based on the result of the antenna evaluation.
More specifically, when the SNR of a beacon (beacon 1) received via the first antenna in use becomes lower than a predetermined value, a station (STA) switches to the second antenna. The STA compares the SNR of beacon 1 received via the first antenna with the SNR of a next beacon (beacon 2) received via the second antenna. If the SNR of the first antenna is higher than that of the second antenna, the STA switches back to the first antenna and continues the communication; otherwise, the STA continues the communication using the second antenna. As described above, the STA evaluates each antenna, determines a selected antenna, and continues the communication.
However, if the antenna evaluation process starts, and a switch to the second antenna is made, the STA cannot transmit/receive a data packet until the selected antenna is determined.
This causes the AP to retransmit the data packet many times. The AP which has retransmitted a predetermined number of times (a predetermined period of time) or more determines that it is impossible to communicate with the STA, and disconnects the communication.
As described above, if the diversity function executes the antenna evaluation process, it may occur that retransmission of a data packet is repeated until the antenna evaluation process is completed, which causes the communication to be disconnected.